Ontopia is a set of tools for building applications driven by Topic Maps, such as Web portals. The main benefit of Topic Maps is that they provide a flexible and expressive data model supporting much better findability than traditional solutions, as well as advanced features like automated merging of datasets.
tmphoto is a Web photo gallery with a fairly advanced metadata structure, allowing photos to be described in terms of place, category, persons in the photo, and events. The places, categories, persons, and events can be further described. It offers a nice browsing interface based on the metadata.
Duke is a fast and flexible record linkage engine. It does not use the traditional blocking (sort by key) approach, but instead relies on Lucene. This makes it high-performance (able to process 1,000,000 records in ~10 minutes). Duke can be run from the command line, but also has an API allowing incremental linking applications to be built easily. It supports reading data from CSV, JDBC, SPARQL, and NTriples, and also supports a number of string comparators and string normalizers.